When circuit boards, or an electronic part, such as an IC chip, and a circuit board are electrically connected, anisotropic conductive adhesives in which conductive particles are dispersed are used. These adhesives are located between opposed electrodes, and the electrodes are connected by heating and pressurization. Then, conductivity in the direction of pressurization is provided and thereby electrical connection and fixing are provided.
For example, metal particles having conductivity, and plated conductive particles obtained by forming a metal coating on the particle surfaces of a core material by electroless plating are used as the above conductive particles.
These conductive particles are required to be always monodisperse. But, the conductive particles may often cause secondary aggregation due to an external factor, such as humidity, oxidation, self-weight, or impact, depending on the storage environment, though the conductive particles are monodisperse immediately after manufacturing.
When the anisotropic conductive adhesive comprises such secondarily aggregated conductive particles, the secondarily aggregated conductive particles dispersed between the electrode spaces easily cause a short circuit.
Also, when the secondarily aggregated conductive particles are dispersed in kneading with the binder, treatment with a strong shearing force for a long time is necessary, and therefore, the deformation and breakage of the conductive particles, and the peeling off of the coating occur. Further, the curing of the epoxy proceeds due to heat generation caused by the kneading, and therefore, it is desired to perform the treatment with a short kneading time.
As methods for suppressing the aggregation of conductive particles, for example, the following Patent Document 1 proposes a method for coating the surfaces of conductive particles with polymer electrolyte thin films, such as a polyanion thin film and a polycation thin film, the following Patent Document 2 proposes a method for coating the surfaces of conductive particles with insulating hollow particles, the following Patent Document 3 proposes a method for fixing insulating inorganic fine particles, in a buried state, to particles coated with a conductive metal, the insulating inorganic fine particles having a particle diameter in the range of ⅓ to 1/100 of the diameter of the coated particles, and the following Patent Document 4 also proposes a method for providing an inorganic insulating layer on the surfaces of plated conductive particles. However, further, a conductive powder in which the aggregation of conductive particles is suppressed and which is also excellent in electrical reliability is desired.
Also, the following Patent Document 5 and the following Patent Document 6 propose modified electroless plated powders in which fine amorphous silica is deposited and coated on electroless plated powder surfaces.    Patent Document 1: Japanese Patent Laid-Open No. 2003-317827    Patent Document 2: Japanese Patent Laid-Open No. 2005    Patent Document 3: Japanese Patent Laid-Open No. 07-118617    Patent Document 4: Japanese Patent Laid-Open No. 2007-510268    Patent Document 5: Japanese Patent Laid-Open No. 2-15176    Patent Document 6: Japanese Patent Laid-Open No. 1-116083